Haptics is a tactile and force feedback technology that takes advantage of a user's sense of touch by applying haptic feedback effects (i.e., “haptic effects”), such as forces, vibrations, and motions, to the user. Devices, such as mobile devices, touchscreen devices, touchpad devices and personal computers, can be configured to generate haptic effects. In general, calls to embedded hardware capable of generating haptic effects (such as actuators) can be programmed within an operating system (“OS”) of the device. These calls specify which haptic effect to play. For example, when a user interacts with the device using, for example, a button, touchscreen, touchpad, lever, joystick wheel, or some other control, the OS of the device can send a play command through control circuitry to the embedded hardware. The embedded hardware then produces the appropriate haptic effect.
In an automotive environment, haptics can provide tactile feedback to help create a more confident and safe user experience in an automotive environment. Automotive applications of haptics have included rotary knobs, joysticks, touchpads and touchscreens. The use of touchscreens in the automotive environment is increasing. Touchscreens are a natural interface for navigation systems, and tactile feedback improves the overall touchscreen usability as well as specific features of the navigation system human-machine interface. Users experience more intuitive interactions, reduced glance time for improved safety, and space-saving designs. The touchscreen buttons deliver a tactile pulse the user can actually feel through the touchscreen, since the touchscreen is mounted on a suspension that permits movement of the touchscreen, allowing the user to select an icon with a quick glance and touch of the touchscreen. Furthermore, with the use of proximity-sensing technology, a hand can be detected as it approaches the touchscreen. When the icon is pressed, the touchscreen pulses to acknowledge the command, allowing one to keep their eyes safely on the road. Thus the physical feedback of a haptic touchscreen or touchpad allows the driver to operate the system without looking at the touchscreen or pad. The Cadillac CUE and the Acura RLX On-Demand Multi-Use Display™ are two automotive haptic touchscreen applications. The Lexus NX utilizes a haptic touchpad application.
The touchscreens used in the automotive environment are large displays and can be heavier than other haptic touchscreens. For example, a 10-inch display may be desired and can weigh around 500 g since the system may include a LCD secured to the touch panel by optical bonding for better visibility. The touchscreen or panel may be referred to as a floating screen, as it is mounted on a suspension system to allow the touchscreen to move as the haptic effects are generated. To provide haptics to a floating system device, low travel or motion and high force for acceleration is required. As moveable masses, such as the touchscreen and its assembly, become larger and/or heavier, the force required rises above what cost effective solenoids or push-pull actuators can provide. As a result, multiple solenoids or push-pull actuators have been needed to produce this required force which is not cost effective and takes up too much real estate. Thus there is a need for an actuator amplification mechanism that can move heavy moveable masses with a greater force to generate the required displacement and acceleration needs.
Another issue in current actuation technology is the need for a more efficient and cost effective braking mechanism. Currently braking can be done through the process of active braking. This is done by sending a reverse signal to the same actuator that was used to move the mass initially. However, the problem with this method is that it is very difficult to implement due to the measurement requirements needed to send an accurate reverse signal. Not only are the measurements and calculations very difficult to obtain, but the braking force that is created is limited by the strength of actuator and its capabilities. As a result, this only creates a limited braking force which will permit the moveable mass to continue moving or oscillating before coming to a complete rest.
Others have also tried to solve this problem through passive friction braking. This is accomplished where a material attached to the fixed mass is pressed onto a material attached to the moveable mass, causing a friction force that opposes travel as the moveable mass moves in relation to the grounded mass. This causes the moveable mass to decelerate once the actuation force is removed. The friction between these two materials is controlled by the force applied normal to the friction surface and by the static and dynamic friction coefficient of the two materials rubbing against each other. However this also can be very difficult to implement because friction needs to be applied to the moveable mass, and this friction force can drastically vary with the force applied normal to the surface. Further, this solution can be difficult to implement because it requires the use of a stronger actuator because the friction force is always opposing motion throughout the duration of the haptic effect. Thus there is also a need for a braking mechanism that can provide more effective braking that does not have such limitations.